1. Field of the Invention
The present invention relates to expandable sand screens and other expandable tubulars. More particularly, the present invention relates to a profiled encapsulation for use with an expandable sand screen or other expandable downhole apparatus. The profiled encapsulation houses instrumentation lines or control lines in a wellbore.
2. Description of Related Art
Hydrocarbon wells are typically formed with a central wellbore that is supported by steel casing. The steel casing lines the borehole formed in the earth during the drilling process. This creates an annular area between the casing and the borehole, which is filled with cement to further support and form the wellbore.
Some wells are produced by perforating the casing of the wellbore at selected depths where hydrocarbons are found. Hydrocarbons migrate from the formation, through the perforations, and into the cased wellbore. In some instances, a lower portion of a wellbore is left open, that is, it is not lined with casing. This is known as an open hole completion. In that instance, hydrocarbons in an adjacent formation migrate directly into the wellbore where they are subsequently raised to the surface, possibly through an artificial lift system.
Open hole completions carry the potential of higher production than a cased hole completion. They are frequently utilized in connection with horizontally drilled boreholes. However, open hole completions present various risks concerning the integrity of the open wellbore. In that respect, an open hole leaves aggregate material, including sand, free to invade the wellbore. Sand production can result in premature failure of artificial lift and other downhole and surface equipment. Sand can build up in the casing and tubing to obstruct well flow. Particles can compact and erode surrounding formations to cause liner and casing failures. In addition, produced sand becomes difficult to handle and dispose at the surface. Ultimately, open holes carry the risk of complete collapse of the formation into the wellbore.
To control particle flow from unconsolidated formations, well screens are often employed downhole along the uncased portion of the wellbore. One form of well screen recently developed is the expandable sand screen, designated by the Assignee as ESS®. In general, the ESS is constructed from three composite layers, including a filter media. The filter media allows hydrocarbons to invade the wellbore, but filters sand and other unwanted particles from entering. The sand screen is connected to production tubing at an upper end and the hydrocarbons travel to the surface of the well via the tubing. The sand screen is expanded downhole against the adjacent formation in order to preserve the integrity of the formation during production.
A more particular description of an expandable sand screen is described in U.S. Pat. No. 5,901,789, which is incorporated by reference herein in its entirety. That patent describes an expandable sand screen which consists of a perforated base pipe, a woven filtering material, and a protective, perforated outer shroud. Both the base pipe and the outer shroud are expandable, and the woven filter is typically arranged over the base pipe in sheets that partially cover one another and slide across one another as the sand screen is expanded, or is expanded directly. The expanded tubular or tool can then be expanded by a cone-shaped object urged along its inner bore or by an expander tool having radially outward extending rollers that are fluid powered from a tubular string. Using expansion means like these, the expandable tubular or tool is subjected to outwardly radial forces that urge the expanding walls against the open formation or parent casing. The expandable components are stretched past their elastic limit, thereby increasing the inner and outer diameter of the tubular.
A major advantage to the use of expandable sand screen in an open wellbore like the one described herein is that once expanded, the annular area between the screen and the wellbore is mostly eliminated, and with it the need for a gravel pack. Typically, the ESS or other solid expandable tubular is expanded to a point where its outer wall places a stress on the wall of the wellbore, thereby providing support to the walls of the wellbore to prevent dislocation of particles. Solid expandable tubulars are oftentimes used in conjunction with an expandable sand screen to provide a zonal isolation capability.
In modern well completions, the operator oftentimes wishes to employ downhole tools or instruments. These include sliding sleeves, submersible electrical pumps, downhole chokes, and various sensing devices. These devices are controlled from the surface via hydraulic control lines, electrical control lines, mechanical control lines, fiber optics and/or a combination thereof. For example, the operator may wish to place a series of pressure and/or temperature sensors every ten meters within a portion of the hole, connected by a fiber optic control line. This line would extend into that portion of the wellbore where an expandable sand screen or other solid expandable tubular or tool has been placed.
In order to protect the control lines or instrumentation lines, the lines are typically placed into small metal tubings which are affixed external to the expandable tubular and the production tubing within the wellbore. In addition, in completions utilizing known non-expandable gravel packs, the control lines have been housed within a metallic rectangular cross-sectioned container. However, this method of housing control lines or instrumentation downhole is not feasible in the context of the new, expandable completions now being offered.
First, the presence of control lines behind an expandable tubular interferes with an important function, which is to provide a close fit between the outside surface of the expandable tubular, and the formation wall. The absence of a close fit between the outside surface of the expandable tubular and the formation wall creates a vertical channel outside of the tubular, allowing formation fluids to migrate between formations therein. This, in turn, causes inaccurate pressure, temperature, or other readings from downhole instrumentation, particularly when the well is shut in for a period of time, or may provide a channel for erosive wear.
There is a need, therefore, for an encapsulation for control lines or instrumentation lines which is not rectangular in shape, but is profiled so as to allow a close fit between an expandable tubular and a formation wall or parent casing. There is further a need for an encapsulation which resides between the outside surface of an expandable and the formation wall, and which does not leave a vertical channel outside of the expandable tubular when it is expanded against the formation wall. Still further, there is a need for such an encapsulation device which is durable enough to withstand abrasions incurred while being run into the wellbore, but which is sufficiently deformable as to be deformed in arcuate fashion as to closely reside between an expanded tubular and the wall of a wellbore, whether cased or open.